No true Scotsman fallacy

"No true Scotsman" is a story used by the philosopher Antony Flew to illustrate a very common fallacious argument, often used by apologists to take advantage of the ambiguity of the definition of a certain key word (or words) in their argument.

Scotsman B: "Is that so? I seem to recall my cousin Angus (who is from Scotland) puts sugar in his porridge"

Scotsman A: "Aye... but no true Scotsman puts sugar in his porridge."

The implication is that Angus is not a true Scotsman, despite the fact that he is from Scotland. The fallacy lies in redefining the word "Scotsman" in order to exclude those who put sugar in their porridge.

Similarly, apologists argue that Christians are good people by categorically denying that anyone who does a bad deed is a "true Christian". The lack of a generally accepted definition of "Christian" allows apologists to redefine the word to fit their arguments. For this reason, many self-professed Christians who commit bad deeds are excluded from the group by apologists.

Since the Scotsman fallacy relies on ambiguity in the definition of the word "Scotsman", it is a form of equivocation.

Erosion by Qualification

In his work on apologetics, Flew discusses the value of the No True Scotsman fallacy in its qualification of excluding members of a group from that group on the basis of their membership being undesirable. It is often a response to ad hominem attacks on a religious institution, or attacks on the moral standing of such an institution, on the basis that its members partake in activities the organization condemns.

For example:

Apologist: No Christian could ever commit genocide.

"Interlocutor:" Well, Adolf Hitler was a Christian, and he committed genocide. Ipso facto, it is the case that some Christian has committed genocide, and so some Christian can commit genocide.

"Apologist:" Adolf Hitler was not a 'true' Christian, because that behavior is not consistent with living a Christ-like life.

In this case, there is a requalification of the word Christian. The interlocutor takes it to mean something to the effect of "professes a belief in the Nicene Creed" or "accepts the proposition that Jesus Christ was crucified and resurrected in order to serve some great cosmological purpose that makes him worth worshipping." The apologist then asserts that those things are not sufficient conditions for being a "true" Christian. Rather, the necessary condition is "living a Christ-like life."

The move that Flew asserts is best is a move to clarify the definition of the term:

"Interlocutor:" Well, then what are the conditions for being considered a 'true' Christian?

The intention of the move is to establish the exact definition. If one asserts that the definition of a 'true' Christian is predicated on behavior, then the statement "No Christian could ever commit genocide" because true a priori. However, the qualification also calls into question the legitimacy of the label. Flew asserts that the over-qualification (having too many conditions) of the group "'true' Christian" causes it to become less meaningful to the discourse, and allows for a number unprecedented moves, wherein individuals belonging to any group get to renounce the group's liability for the crimes of the members of the groups, like so:

"Nazi Sympathizer:" No Nazi could ever commit genocide.

"Interlocutor:" Well, Adolf Hitler was a Nazi, and he committed genocide, etc.

"Nazi Sympathizer:" Adolf Hitler was not a 'true' Nazi, because that behavior is not consistent with the principles of National Socialism.

The problem is that what is at issue is the apologist's interpretation of the doctrine of their religion. The apologist interprets Christianity as fundamentally non-violent, and as such eschews all violence, and believes that the institution eschews all violence; however, this conflicts with the interpretations of an enormous number of those who self-identify as Christians. In order to qualify the term "Christian" properly, what really needs to be pressed is some move like this:

"Interlocutor:" Well, then what are the conditions for being considered a 'true' Christian?

"Apologist:" Well, the conditions are a commitment to non-violence and charity and civil service.

"Interlocutor:" And why are those things conditions for being considered a 'true' Christian?

"Apologist:" Because they are a part of the fundamental doctrine of the religion.

"Interlocutor:" That doesn't seem right. Couldn't it be the case that they are a fundamental part of your interpretation of the doctrine of the religion? It doesn't seem that everyone reading the text locates the same interpretation.

There are then two lines for the apologist. Either (1) to concede that the interpretation is subjective, and that adherence to the interpretation is not really an objective metric for including or excluding people from the group or (2) to insist that their interpretation is factual and objective, and that membership is conditioned by right conduct and right belief. Either of these moves resolves the fallacy.